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Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells.

Zhang N, Chen FY, Wu XQ - Sci Rep (2015)

Bottom Line: It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR).The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster.This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian 710072, China.

ABSTRACT
The structure of 38 atoms Ag-Cu cluster is studied by using a combination of a genetic algorithm global optimization technique and density functional theory (DFT) calculations. It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR). The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster. This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

No MeSH data available.


Related in: MedlinePlus

Global optimization structure found by GA at the atomistic potential level: (a) The bulk-like truncated octahedron cluster for Ag38, (b) the polyicosahedral core-shell cluster for Ag32Cu6 and (c) the TO core-shell isomer for Ag32Cu6. (d) Low energy structure for TO Ag32Cu6 core-shell cluster after DFT local reoptimization. Each structure is shown in two views with two styles. Ag atoms are reprented in blue and Cu atoms are reprented in light red.
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f2: Global optimization structure found by GA at the atomistic potential level: (a) The bulk-like truncated octahedron cluster for Ag38, (b) the polyicosahedral core-shell cluster for Ag32Cu6 and (c) the TO core-shell isomer for Ag32Cu6. (d) Low energy structure for TO Ag32Cu6 core-shell cluster after DFT local reoptimization. Each structure is shown in two views with two styles. Ag atoms are reprented in blue and Cu atoms are reprented in light red.

Mentions: Figure 1(b) compares the Δ1 and Δ2 for the lowest-energy 38-atom clusters with different Ag atom numbers, from which we can single out the especially stable composition at n = 30 and 32 Ag atoms. For these clusters, the minima in Δ1 and maxima in Δ2 are found to concur. These locally stable structures are Ag30Cu8 and Ag32Cu6 clusters. As shown in Fig. 2, Ag32Cu6 cluster has the perfect core-shell pIh structure where Cu atoms forming a ring, and is completely covered by a single layer thick Ag shell. Morever, the Ag32Cu6 cluster has the highest D6h symmetry of the whole sequence of the heterogeneous clusters. Ag30Cu8 cluster, as shown in Figure S1, is a disordered core-shell structure with a low symmetry of Cs which includes the maximum number of small atoms inside, that is to say, 8-Cu-atom core is embedded in a 30-Ag-atom shell. Thus, Ag32Cu6 with D6h symmetry is a magic core-shell cluster for the 38-atom Ag-Cu clusters. Liking other magic clusters, the pIh-Ag32Cu6 cluster has several common features, i.e., a high-symmetry core-shell atomic order and complete geometry shape.


Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells.

Zhang N, Chen FY, Wu XQ - Sci Rep (2015)

Global optimization structure found by GA at the atomistic potential level: (a) The bulk-like truncated octahedron cluster for Ag38, (b) the polyicosahedral core-shell cluster for Ag32Cu6 and (c) the TO core-shell isomer for Ag32Cu6. (d) Low energy structure for TO Ag32Cu6 core-shell cluster after DFT local reoptimization. Each structure is shown in two views with two styles. Ag atoms are reprented in blue and Cu atoms are reprented in light red.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493688&req=5

f2: Global optimization structure found by GA at the atomistic potential level: (a) The bulk-like truncated octahedron cluster for Ag38, (b) the polyicosahedral core-shell cluster for Ag32Cu6 and (c) the TO core-shell isomer for Ag32Cu6. (d) Low energy structure for TO Ag32Cu6 core-shell cluster after DFT local reoptimization. Each structure is shown in two views with two styles. Ag atoms are reprented in blue and Cu atoms are reprented in light red.
Mentions: Figure 1(b) compares the Δ1 and Δ2 for the lowest-energy 38-atom clusters with different Ag atom numbers, from which we can single out the especially stable composition at n = 30 and 32 Ag atoms. For these clusters, the minima in Δ1 and maxima in Δ2 are found to concur. These locally stable structures are Ag30Cu8 and Ag32Cu6 clusters. As shown in Fig. 2, Ag32Cu6 cluster has the perfect core-shell pIh structure where Cu atoms forming a ring, and is completely covered by a single layer thick Ag shell. Morever, the Ag32Cu6 cluster has the highest D6h symmetry of the whole sequence of the heterogeneous clusters. Ag30Cu8 cluster, as shown in Figure S1, is a disordered core-shell structure with a low symmetry of Cs which includes the maximum number of small atoms inside, that is to say, 8-Cu-atom core is embedded in a 30-Ag-atom shell. Thus, Ag32Cu6 with D6h symmetry is a magic core-shell cluster for the 38-atom Ag-Cu clusters. Liking other magic clusters, the pIh-Ag32Cu6 cluster has several common features, i.e., a high-symmetry core-shell atomic order and complete geometry shape.

Bottom Line: It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR).The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster.This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian 710072, China.

ABSTRACT
The structure of 38 atoms Ag-Cu cluster is studied by using a combination of a genetic algorithm global optimization technique and density functional theory (DFT) calculations. It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR). The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster. This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

No MeSH data available.


Related in: MedlinePlus